Technical Field
The present disclosure relates to three dimensional imaging using the structured light approach, and more particularly to ocular surface measurement over the anterior surfaces of the cornea and sclera.
Description of Related Art
The accurate knowledge of the corneal surface is very important for diagnostics and treatment of a number of ocular conditions. Cornea is responsible for about 70% of the refractive power of the eye and therefore the corneal topography has a great importance in determining the quality of vision. It is commonly used for diagnosis of keratoconus, for selecting appropriate soft contact lenses, for fitting scleral lenses, and for topography guided Laser-Assisted in situ Keratomileusis (LASIK).
Currently the majority of the corneal topography is performed using a Placido disk. The concept of the Placido disk was introduced by Antonio Placido in 1880 and since then it has been the primary method for corneal topography. The method is based on viewing or imaging the corneal reflection of series of concentric bright and dark rings positioned in front of the cornea. By increasing the number of concentric disks and placing them on a concave surface around the eye, it is possible to measure a large section of the cornea. But in most cases the data on the central zone needs to be interpolated and the data on the corneal periphery is often missing due to limited reflection. Additionally, Placido disks are not capable of measuring the scleral topography, which is important for custom fitting of scleral lenses.
In addition to the Placido disk, scanning slit systems, such as the Orbscan II by Bausch & Lomb, Scheimpflug systems such as the Galilei by Zeimer Ophthalmic Systems, and rastersterographic systems such as the CTS by Par Technlogies have been used for corneal topography. While these systems provide better measurement of the corneal apex they lack the coverage of the corneal periphery and sclera needed for scleral lens fitting.